1. Field of the Invention
This invention relates to a variable damping and stiffness structure having a variable damping device provided in a frame of the structure and interconnecting a frame body and a variable stiffness element or variable stiffness elements themselves provided in the frame, wherein an external vibrational force or disturbance like an earthquake and wind is controlled by a computer according to the vibration of the structure to thereby reduce the response amount of the structure.
2. Description of the Prior Art
The present applicant has proposed various active seismic response control systems and variable stiffness structures (for example, Japanese Patent Laid-open No. Sho 62-268479 and U.S. Pat. No. 4,799,339), in which a variable stiffness element in the form of a brace and a wall or the like is incorporated into a post-beam frame of the structure, and the stiffness of the variable stiffness element itself or the connecting condition of a frame body and the variable stiffness element is varied to analyze the property of an external vibrational force like an earthquake and wind by a computer, so that the stiffness of the structure is varied to provide unresonance with the external vibrational force to achieve the safety of the structure.
Now, conventional active seismic response control systems observe mainly the relationship between a predominant period of the seismic motion or the like and a natural frequency (usually, the primary natural frequency is often taken into consideration) of a structure, wherein a resonance phenomenon is avoided by offsetting actively the natural frequency of the structure relative to the predominant period to thereby improve the reduction in the response amount.
However, since the seismic motion or the like is particularly non-stationary vibrations, it is conceivable that the conventional active seismic response control system does not necessarily carry out the optimal control in the case where the predominant period is indistinct or a plurality of predominant periods are present, for example.